Drug resistance means the decreased efficacy of the drug treatment on disease or symptoms. When the drug concentration is not efficient to kill or inhibit the pathogens, the residual pathogens may have resistance to this kind of drug. For example, the bacteria may have drug resistance because antibiotics generated reactive oxygen and then induced DNA mutations.
The mechanism of antibiotics drug resistance is basically controlled by genes; these genes are collectively referred to as drug resistance gene. With respect to these resistance genes, some bacteria are born to have these genes, some may be obtained from other bacteria through the plasmid or transposons. Antibiotics will kill the bacteria under natural environment, but the bacteria with drug resistant genes won't be killed. That means, there will be more and more bacteria with drug resistant genes in the antibiotic environment. Therefore, the more use of antibiotics, the higher proportion of antibiotic-resistant bacteria will be.
Recently, the strong drug resistance bacteria were generated more and more. This phenomenon is because the lack of effective drug to treatment for drug resistant bacteria and excessive abuse of the antibiotics, which results in more than 40,000 deaths each year in Europe and North America. Thus, all the countries are developing new antibiotics to kill the “superbugs” resistant bacteria.
Ampicillin is used as a first-line antibiotic, in clinical, which is commonly used in medical institutes and livestock industry, and thus result in the abuse of antibiotics to induce the antibiotic resistance.
The outpatients of the E. coli present 71% drug resistance to ampicillin in Taiwan, and 39.3% in United States. This situation is not only for the first-line antibiotics, but also for most antibiotics. For example, Vancomycin was used only after all other ineffective antibiotics had been treated, which is also been abused recently and generating drug resistant bacteria, such as Vancomycin-Resistant Enterococcus (VRE).
However, the pharmaceutical companies aim on saving costs on research and development, thus using easy method on developing drugs, such as simply modifying the structure of drug compound. For example, replacing the functional group of compound. After using for a time period, the bacteria would generate antibiotic resistance to the modified drugs easily. That is, if there is no new antibiotics been developed, there will be no any effective drug for treating bacteria so as to induce severe bacterial infection and the patient will be incurable.